Black Spot of Rose presentation 2012

1. By
Sloane Lane

2. Scientific Name:
Diplocarpon r rose

3. The Life Cycle
of
Black Spot of Rose

4. Rose Black spot is also known as Diplocarpon rosae. The
fungus Diplocarpon rosae is the causal organism of rose
black spot, Diplocarpon rosae is classified as an ascomycete
in the family Dermateaceae and is a hemibiotrophic fungus
that is restricted to the genus Rosa L. It is spread primarily
through waterborne, two-celled asexual spores (conidia) that
require free water to germinate.

5. • Black spot fungus over winters on infected leaves, or on the plant and
on dropped leaves.
• It can also remain in infected stems.
• In the Spring, the fungus produces spores which are carried by rain
splashes to new bushes, starting the infection on new leaves.
• Spores are produced throughout the growing season, causing repeated
cycles of infection.
• Young, growing leaves are particularly susceptible.
• The fungus is spread by wind, driven rain, splashed irrigation water
and on garden tools.
In warm weather the fungus can affect leaves that have been wet for as
little as 7 hours. Leaf spots begin to show 4 -5 days after the initial
infection.

6.  Leaves are most susceptible while still expanding after bud break.
 The fungus spores must be immersed in water continuously for seven hours for
germination and infection to occur.
 Fungal spores can be spread by splashed water, or fallen leaves that may
disperse the fungal pathogen.
 The fungal pathogen is present only in the lesion, but its damage extends
throughout the leaf.
 The spot lesions are often small and rarely kill the rose branches, but these are
extremely important in the survival of the fungal pathogen over-wintering
from season to season.
 This fungal pathogen can be spread to surrounding plants, including citrus
trees, ornamentals, and some other garden variety's.
Cultural conditions that favor disease development include dense plantings, and
watering late in the day when water will remain on plant foliage for many
hours, and not allowing good air circulation can also contribute to this fungus.

7. The Host
Healthy
Rose

8. Unhealthy
Rose Bush
with Black
Spot of Rose

9. Description:
Black spot is a nasty
fungus disease of roses.
Infected leaves have black,
rounded spots on the
upper surface of the
leaves. The spots have
feathery or fringed edges
often with a yellowish halo
around the spots. In
severe infections, the
spots are large and run
together. Eventually, the
leaves turn yellow and
drop. Sometimes, flower
pedals are also affected.

10. . Overtime this can produce a
weakened bush on which cane
dieback and stem cankers can form,
and winter injury can become
severe and can predispose the plant
to insect attacks, and other diseases.

11.  The Rose Industry over the years have been
able to find measures to keep their field
losses down with preventive measures, and
routine disease management. This disease
is less of a problem in greenhouses where
relative humidity can be carefully
controlled. Susceptible landscape roses
must be sprayed frequently with fungicides
to keep the disease under control.
Fortunately for rose growers many breeders
are constantly striving to produce disease
resistant plants and many of the roses
introduced during the past decade have
shown a remarkable improvement in overall
resistance to infection.

12. Treat the bush with preventive sulfur spray
in spring, before new growth. The use of
sulfur to fight black spot is well known and
proven. The spores won't grow on sulfur but
because it washes off you must repeat the
application on a regular basis and after each
rain.

13. There are also many home-made solutions which different
gardeners live by if you choose to go organic. Many methods
being practiced are with the solutions varying from
aspirin, backing soda, and milk, and mild detergents that can
be mixed and used as preventive measures.